Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative therapy for many patients with hematologic malignancies and marrow failure. A critical hurdle in accomplishment of successful HSCT has been graft-versus-host disease (GVHD).The ultimate objective of the research projects in this renewal application is to further improve our understanding of the pathophysiology of aGVHD and cGVHD and to develop novel strategies for both prevention and therapy of cGVHD by targeting distinct cellular populations in these two syndromes while maintaining GVL. Key to achieve this objective and thus to lead to the success of this program project is dynamic biostatistical collaboration with individuals in each of the 3 projects and the 3 other Cores. The purpose of the Biostatistics Core C is to provide the following services that will be utilized by the research projects included in this Program Project. 1. To provide biostatistical collaboration for translational clinical research studies. 2. To provide biostatistical collaboration for translational animal research studies. 3. To provide biostatistical and/or bioinformatics collaboration for translational laboratory research studies. 4. To provide research infrastructure for translational research. 5. To provide computing resources for data processing, and statistical analysis, standardized reporting, and quality control. RELEVANCE (See instructions): Preventing or treating cGVHD, thus reducing related morbidity and mortality, is important because 1) improvements in HSCT technology allow the use of older donors and older patients to receive transplant, thus more patients undergo HSCT, and 2) improvements in supportive care result in better survival in later time periods when cGVHD occurs.